Research has shown that the response of the human ear is very dependent on the frequency content of the sound. The ear has peak response around 2,000 Hz to 4,000 Hz and significantly less response at lower and higher frequencies. In other words, a sound with a frequency between 2,000 Hz and 4,000 Hz will be perceived as louder to the ear than sounds below and above this range. Additionally, the ear's ability to perceive low and high frequencies varies with sound intensity (i.e., volume) level. This explains why soft music seems to sound less rich than music played at higher volume. Turning to FIG. 1, each curve represents a different volume level from a sound source, such as a stereo system. Curves on the bottom represent quieter volume levels and curves on the top represent louder volume levels. By examining these curves it will be observed that the quieter a volume level the greater the difference in sound intensity level (sound energy) required for the ear to hear low and high frequencies. Thus, it is desirable for a sound system to compensate for the natural inadequacies of the ear.
Furthermore, the ability of a typical speaker to reproduce sound diminishes (rolls-off) at low and high frequencies resulting in a reduction of sound content conveyed to the ear. A significant reduction of sound intensity occurs as the signal frequency decreases from 700 Hz down to 20 Hz and again as the frequency increases from 4,000 Hz to 20,000 Hz. See for example the typical speaker frequency response illustrated graphically in FIG. 2. This roll-off results in diminished loudness and thus audibility as perceived by the human ear.
One method/apparatus of solving the low frequency problem in the prior art, is to provide a subwoofer system. Subwoofer systems, specifically designed to accentuate lower frequencies, are incorporated with standard stereo systems to compensate for the low frequency roll-off. A major problem is that commonly obtainable audio subwoofer systems for reproducing low frequency sound are constructed in such an embodiment that their form is bulky and therefore cannot be easily transported for personal use, for example with a portable media player when walking or exercising. Additionally, commercially obtainable subwoofer systems consume sizeable electrical power, require ventilation for heat removal, can be complex and difficult to connect and operate, are costly to obtain, present a potential for electrical shock when exposed in damp or wet environments, and as a result are not able to be proliferated widely or easily.
A further method of solving the low frequency problem in the prior art, is to remove or diminish the magnitude of low frequency sounds and replace them with harmonics of the natural frequency providing a virtual simulation of the natural low frequency.
A major problem is that natural low frequencies near or below 50 HZ (i.e. Sub-Bass frequencies) have desirable characteristics, such as the ability to convey physical sensation (feeling). Many sound effects used in movies, video games, and music genre's fall into this frequency range including; explosions, earthquakes, crashes, gunfire, and electronically produced deep bass musical tones and rhythms. Therefore, removing or diminishing these frequencies results in an incomplete audio reproduction experience.
To date, audio engineers have been unable to produce extreme low frequency sound (i.e., in the bass and sub-bass range, 50-250 Hz and below 50 Hz respectively) from all speaker and earpiece types of sound devices. In fact, it is commonly believed by audio engineers that it is physically impossible to produce extreme low frequency sound with small speakers and other audio sound devices.
It would be highly advantageous, therefore, to remedy the foregoing and other deficiencies inherent in the prior art.
Accordingly, it is an object of the present invention to provide a new and improved low frequency sound enhancement system.
It is a further object of the present invention to provide a new and improved dynamic sound enhancement system that substantially compensates for the natural inadequacy of the human ear at either or both the low frequencies and the high frequencies.
It is a further object of the present invention to provide a new and improved dynamic sound enhancement system that substantially compensates for the roll-off effects of standard speakers and other sound producing devices.
It is a further object of the present invention to provide a new and improved dynamic sound enhancement system that is capable of being used with substantially any sound producing devices, including speakers, small speakers, earpieces, hearing aids, etc.